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Subject: Re: Ftrace: can trace kthread?
From: "Figo.zhang" <zhangtianfei@leadcoretech.com>
To: Yong Zhang <yong.zhang0@gmail.com>
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> > i try by set_ftrace_pid, it also can't ftrace the kswapd.
> 
> Are you sure kswapd got chance to run on your system?
> 
> BTW, I can successfully trace bdi_writeback_thread,
> # tracer: function
> #
> #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
> #              | |       |          |         |
>        flush-8:0-374   [000] 600743.828496: finish_task_switch <-schedule
>        flush-8:0-374   [000] 600743.828498: perf_event_task_sched_in
> <-finish_task_switch
>        flush-8:0-374   [000] 600743.828498: del_timer_sync <-schedule_timeout
>        flush-8:0-374   [000] 600743.828499: try_to_del_timer_sync
> <-del_timer_sync
>        flush-8:0-374   [000] 600743.828499: lock_timer_base
> <-try_to_del_timer_sync
>        flush-8:0-374   [000] 600743.828499: _spin_lock_irqsave <-lock_timer_base
>        flush-8:0-374   [000] 600743.828500: _spin_unlock_irqrestore
> <-try_to_del_timer_sync
>        flush-8:0-374   [000] 600743.828500: kthread_should_stop
> <-bdi_writeback_task

are you use my scprit to trace the bdi_writeback_thread ?